The inventions disclosed herein relate generally to performing storage operations on electronic data in a computer network. More particularly, aspects of the present invention relate to data transmission schemes used during a storage operation including data pathways and other components used in the transfer of data.
Over time, storage of electronic data has evolved through many forms. During the early development of the computer, data storage was limited to individual computers. Electronic data was stored in the Random Access Memory (RAM) or some other storage medium such as a hard drive or tape drive that was an actual physical part of the individual computer.
Later, with the advent of network computing, storage of electronic data gradually migrated from individual computers to stand-alone storage devices accessible via a network. Over time, these individual network storage devices evolved into more complex systems including networks of tape drives, optical libraries, Redundant Arrays of Inexpensive Disks (RAID), CD-ROM jukeboxes, and other devices. Common architectures included drive pools, which generally are logical collections of drives with associated media groups including the tapes or other storage media used by a given drive pool.
Serial, parallel, Small Computer System Interface (SCSI), or other cables directly connect such stand-alone storage devices to individual computers that are part of a network of other computers such as a Local Area Network (LAN) or a Wide Area Network (WAN). Generally, each individual computer on the network controlled the storage devices that were physically attached to that computer and could also access the storage devices of the other network computers to perform backups, transaction processing, file sharing, and other storage-related operations.
Network Attached Storage (NAS) is another storage scheme using stand-alone storage devices in a LAN or other such network. In NAS, a storage controller computer typically controls the storage device to the exclusion of other computers on the network, but the SCSI or other cabling directly connecting that storage device to the individual controller is eliminated. Instead, storage devices are directly attached to the network itself.
Yet another network storage scheme is modular storage architecture which is more fully described in U.S. Pat. No. 7,035,880 and U.S. Pat. No. 6,542,268. An example of such a software application is the Galaxy™ system, by CommVault Systems of Oceanport, N.J. The Galaxy™ system is a multi-tiered storage management solution which includes, among other components, a storage manager, one or more media agents, and one or more storage devices. The storage manager directs storage operations of client data to storage devices such magnetic and optical media libraries. Media agents are storage controller computers that serve as intermediary devices managing the flow of data from client information stores to individual storage devices. Each storage device may be uniquely associated with a particular media agent and this association may be tracked by the storage manager.
A common feature shared by all of the above-described network architectures is the substantially static relationship between storage controller computers and storage devices. In these traditional network architectures, storage devices are generally connected, virtually or physically, to a single storage controller computer. Generally, only the storage controller computer to which a particular device is physically connected has read/write access to that device. One computer typically cannot control the drive pool and media group be that is being controlled by another. Requests to store and retrieve data from such a drive pool and media group would have to be coordinated by the controlling computer. Typically, storage media reserved or being written to by one media agent cannot be written to be another media agent. Thus, often storage media being used pursuant to one storage policy cannot be used by another storage policy and vice versa often resulting in the inefficient use of storage resources.
In some prior art systems, storage policies may specify alternate data paths or resources in the case device failure or an otherwise unavailable data path. However, such systems typically specify a single alternate data path. Moreover, because backup operations are traditional performed on a client by client basis, each client may store information on different media, resulting in inefficient media use. Furthermore, in many systems, failover conditions often result in the use of additional media further resulting in inefficient use of resources. In addition, alternate data paths are defined in a static fashion, and thus conventional data protection schemes are unable to adapt to changing network conditions.